The aim of this study was to evaluate the efficacy and side effects of zuclopenthixol acetate compared with haloperidol in the management of the acutely disturbed schizophrenic patient. Suitable subjects diagnosed as having schizophreniform disorder or acute exacerbation of schizophrenia admitted to the psychiatric wards Hospital Kuala Lumpur were randomised to receive either zuclopenthixol acetate or haloperidol. They were rated blind for three consecutive days using the Brief Psychiatric Rating Scale (BPRS), Clinical Global Impression (CGI) and UKU Side Effects Scale. Apart from repeat injections of the same medication, no other anti-psychotic was given for the duration of the study. 50 subjects entered the study of which 44 completed. 23 were given zuclopenthixol acetate and 21 haloperidol. Both groups significantly reduced BPRS and CGI scores on all 3 days compared to the initial rating (p < 0.001). There was however no difference between the zuclopenthixol acetate and haloperidol group scores on all days (p > 0.05). More subjects on haloperidol than zuclopenthixol required more than 1 injection during the study. Both groups had minimal side effects. Zuclopenthixol acetate was effective in the management of the acutely disturbed schizophrenic.